As color original reading means of an original reading device of a copying machine or a multifunction printer, color original reading means that uses an image sensor including R (red), G (green), and B (blue) color filters that are applied on light receiving elements is known. As the image sensor, a CCD (charge coupled device) image sensor and a CMOS (complementary metal oxide semiconductor) image sensor are available.
In reading an original, an original is illuminated with light by using a light source for reading the original, and light reflected from the original is received by the light receiving elements in the image sensor.
A row of light receiving elements in the image sensor is disposed in a main scanning direction for a desired number of pixels, and three rows of light receiving elements are disposed in a sub-scanning direction so as to be apart from each other by a desired interval. The main scanning direction is a direction in which light receiving elements are disposed side by side in a row, and the sub-scanning direction is a direction orthogonal to the main scanning direction.
The R, G, and B color filters each transmit only light having a wavelength corresponding to the color thereof. The R, G, and B filters decompose light reflected from the original into lights corresponding to the colors thereof. The light receiving elements each receive the light corresponding to the color thereof, and make it possible to read a color image (Patent Literature 1).
As an arrangement of color filters in the main scanning direction, an arrangement in which the R, G, and B color filters are periodically disposed in the main scanning direction of a light-receiving-element row is also known (Patent Literature 2).